The overall goal of this proposal is to identify means for improving ? cell regeneration in the adult pancreas. With previous help of NIH/NIDDK funding we developed a transgenic model of inducible total or partial ? cell ablation (termed RIP-DTR). We have reported that in these mice there is spontaneous reconstitution of new ? cells from heterologous (i.e. non-? cells after near-total ? cell loss. The RIP-DTR model has revealed an unsuspected degree of cellular plasticity in the pancreas of juvenile and adult mice, including aged individuals, regarding the spontaneous inherent capacity of islet ? cells and ? cells to switch to insulin production upon ? cell loss. During the next 5 years we want to address the following fundamental questions: 1. What is (are) the signal(s) driving ? cell reprogramming upon near-total ? cell ablation? 2. Can the ? cell to-? cell conversion be fostered? Why only a small fraction of ? cells engages into conversion? What is the nature of the epigenetic modifications in reprogrammed ? cells? 3. Can human ? cells reprogram to insulin production? 4. What is the influence of ageing on islet cell plasticity? 5. Can other islet cells, i.e. besides ? cells, reprogram to insulin production? Specifically, the proposed aims are as follows: Aim1: Pathways and factors promoting/facilitating ? cell reprogramming in mice and human Aim2: Pathways and factors promoting/facilitating ? cell reprogramming in mice and human Aim3: In vivo (whole body) tissue screening to identify new cell sources with high plasticity potential to convert toward the ? cell phenotype Description of Aims 1 and 2: We previously reported that ? cells do reprogram to insulin production after ? cell loss in adult mice. We have now discovered (MS under revision) that ? cells efficiently reprogram to insulin production after total ? cell loss in prepubescent mice, leading to 100% diabetes recovery. We plan to study: 1- What are the instructive signals and which signaling pathways coordinate ? cell and - ? cell conversion? 2- Why ? cell conversion is temporally restricted to young mice, while ? cell conversion only occurs after puberty? 3- Are ? cell and ? cell conversion mechanisms mutually exclusive? 4- Can in vivo ? cell and ? cell conversions be facilitated by means of compounds mimicking the effect of instructive signals? 5- Are human islets endowed with cell plasticity capabilities? How diabetic conditions influence i) the capacity of human/mouse ? cell and ? cells to reprogram, and ii) the maintenance of the ? cell phenotype? Description of Aim 3: Given the potential clinical impact of cell reprograming considered broadly, we also plan to explore other target cell types for their capacity for trans-fating into a ? cell-like phenotype. We plan to study: 1- What tissues are susceptible of undergoing cell reprogramming? What are the optimal conditions for cell reprogramming in situ? Would ectopic extra-pancreatic beta-like cells function properly? 2- Can transplantable functional insulin-producing cells be obtained ex vivo from patient-derived primary cells?